Ultrahigh frequency generator



March 22, 1938.

R. A. HEISING 2,111,626 ULTRAHIGH FREQUENCY GENERATOR Original Filed Oct. 3, 1935 FIG. 3

0 l2 1 .33 ll?! Win YNVENTOR 14, HE/S/NG BV 4 Patented Mar. 22, 1938 UNITED STATES PATENT oFFicE Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Original application October 3, 1-935, Serial No. 43,298. Divided and this application May 13,

1936, Serial No; 79,485

' 4'Claims. (01-.250-36) This invention relates to electron discharge devices and more particularly to such devices capable of generating and amplifying ultra-high frequency impulses. This application is a division of application Serial No. 43,298, filed October 3,

As isknown inthe art, in electron discharge devices including at least a cathodean anode and a control electrodeor grid the electrons emanat ing from the cathode are subjected to. the potential on the control electrode or grid in their passage to the anode. Inthe present devices the electrons are under the influence of the grid potentials throughout a relatively large distance in the path the electrons traverse in passing tothe anode. At ultra-high frequencies, the time required for theuelectrons to traverse the distance in which they are acted upon by the grid potentials may become too great apart of thecycle at which it is desired to operate the device. To overcome this, it has been proposed to make the electrode spacings extremely small. However, the attainment of such small spacings involves mechanical and electrical difficulties and, furthermore, may necessitate the use of relatively small electrodes so that the power'output obtainable from devices so constructedis relatively small.

In electron discharge devices of conventional construction, at ultra-high frequencies thenrapidly reversing grid potentials cause a large proportion of the electrons emanating from the cathode to execute a to-and-fro or oscillating motion between the grid and the cathode, which motion results in a power loss. Also, as a result of this motion, the passage of some of the electrons from the grid to the anode is not initiated until late in the cycle so that these electrons extract energy from the grid circuit which'is not compensated. for by movement of the electrons away from the grid and to the anode. energy, which is commonly known as the active grid loss, becomes of appreciable'magnitude at ultra-high frequencies.

One'object of this invention is to efiiciently generate impulses of ultra-high frequencies.

Another object of this invention is to reduce the active grid losses iii-electron discharge devices whereby the efficiency of such devices, particularly at ultra-high frequencies, is increased.

A further object of this invention is to enable the use of relatively wide electrode spacings and relatively large electrodes in electron discharge devices adapted for the generation of ultra-high frequency impulses.

In one illustrative embodiment of this inven- The resulting loss of tion, an electron discharge device comprises an incandescible cathode, a plurality of anodes having juxtaposed end portions, and a plurality of control electrode elements disposed between the cathode and the anodes and adapted to influence electron beams from the cathode so that each of the beams impinges alternately upon two of the anodes, to constitute. the device a repeater device of the electron beam type.

- At ultra-high frequencies, a time delay may occur between the potential changes onthe control electrode elements and the corresponding deflections of the electron beams at their points of incidence upon the anodes. In accordance with a feature of this invention the deleterious effects of such time delay are prevented by a shifting in phase of the variable potentials appearing upon the control electrode elements and upon the anodes. For example, either the input or output circuit of .the device may be detuned slightly to provide the proper phase shift. If the device is utilized as an oscillation generator, the input and output circuits may be connected by a transmission line or other delay circuit to provide the proper phase shift inthe potentials upon the control electrode elements and the anodes.

It will be apparent that in devices constructed in accordance with this invention the electrons flowing to the anodes are subjected to the influence of the control electrode throughout but a small portion of the path they traverse in passing to the anodes. The small change of direction of motion of the electrons produced in the vicinity of the control electrodes is multiplied because of the movement of the beams, analogously to the principle of levers, so that a large displacement of the electron beams occurs at their points of incidence upon the anodes. Hence, the electrodes may be relatively widely spaced and the difficulties attendant upon the extremely small electrode spacings used heretofore in ultrahigh frequency devices are obviated.

The invention and the several features thereof will be understood more clearly and fully from the following detailed description with reference to the accompanying drawing in which:

Fig.1 is a diagrammatic view showing the form and arrangement of the electrodes in an electron discharge device illustrative. of one embodiment of. this invention;

Fig. 2 is a diagrammatic viewillustrating another embodiment of this invention wherein the electrodes are arranged coaxially; and

. Fig. 3 illustrates atypical oscillator circuit including an electron discharge device constructed in accordance with this invention and including also a time delay element for providing a phase shift between the potentials upon the control electrode elements and the anodes.

In Figs. 1 and 2, the elements corresponding to the elements in Fig. 3 are given the same numerical designations as in said Fig. 3 although distinguished from each other by use of distinctive subscripts.

Referring now to Fig. 3 of the drawing, the electron discharge device shown therein comprises, generally, a cathode I0, a plurality of anodes II, and a control electrode I2 disposed between the cathode and the anodes. Disposed between the cathode I0 and the control electrode I2 is a focussing electrode I3. Another focussing electrode I4 is positioned between the control electrode I2 and the anodes II. An auxiliary or accelerating electrode I 5 is arranged between the focussing electrode I3 and the control electrode I2.

As shown in Fig. 1, illustrating one of two specific tubes that are adapted to be used with the Fig. 3 circuit, the other of which is illustrated by Fig. 2, the cathode, here identified by I01 to distinguish from the cathode of Fig. 2, may comprise a plurality of filaments connected in series or in parallel, and arranged in a plane. The anodes II1 may be constituted by an indefinite number of flat plates as disclosed disposed at a very small angle to the cathode plane, with adjacent end portions overlapping. Their interconnections to cause them to effectively constitute two anodes will be explained later. The control electrode I21 may include a plurality of pairs of linear metallic wires or rods connected as shown so as to comprise two groups and positioned parallel to the cathode plane and on opposite sides of normals I 9 extending from the cathode plane to the overlapping end portions of the anode plates.

If the anodes II1 of Fig. 1 are operated at a positive potential, electrons will flow from the cathode I01 to the anodes H1 in substantially linear paths and some of the electrons Will pass between the wires or rods of the control electrode and be subject to potentials upon the control electrode. Thus, if the potentials upon the wires or rods are varied, the electron beams passing therebetween will be deflected in accordance with such potential variations and may be caused to impinge alternately upon two of the anode plates as indicated by the broken lines 20.

The accelerating electrode I5 may be com posed of a plurality of flat plates as disclosed disposed parallel to the cathode plane and spaced to form openings or slits in alignment with the normals I9. Alternatively, the accelerating electrode I51 may be a single fiat plate having suitable openings or slits therein. Preferably the electrode I51 is operated at a greater positive potential, relative to the cathode I01, than the potential on the anodes II1 so that the electrons are subjected to a retarding force between the control electrodes I21 and the anodes H1 and, therefore, will have a relatively low velocity when reaching the anodes, whereby a high operating efficiency is obtained.

The electrode I31 may include a plurality of pairs of metallic rods or wires electrically connected together as shown and positioned parallel to the cathode plane and on opposite sides of the normals I9. The rods or wires may be oper ated at either a positive or negative potential, the potential preferably being such that the electron beams are focussed upon the openings or slits in the accelerating electrode I51.

The electrode I41 similarly may be composed of a plurality of pairs of metallic rods or wires electrically connected together as shown and arranged parallel to the cathode plane and on opposite sides of the normals I9. Preferably the electrode I41 is operated at a negative potential of such magnitude that the electron beams are focussed upon the overlapping end portions of the anode plates.

As indicated by the dotted lines 25 in Fig. 1, electrons emanating from the cathode I01, under the influence of the positive potentials upon the anode plates and the plates of the accelerating electrode I51 travel toward the acelerating electrode I51. The electrons are subjected to the field .of the elements of the electrode I31 and are focussed thereby upon the openings or slits of the accelerating electrode and, because of their high velocities, pass through the openings or slits and between the elements of the control electrode I21. If said elements of the control electrode I21 are at the same potential, the electrons tend to spread uniformly after passing the control electrode. This tendency to spread is counteracted by the field of the elements of the electrode I41 and the electrons are concentrated to form beams each focussed uponthe overlapping end portions of the anode plates. If an alternating potential is applied between the elements of the control electrode I21 each of the electron beams will be deflected in accordance with the potential variations and impinge alternately upon two of the anode plates, as indicated by the dotted lines 20, the plates being so connected that the electrons flowing thereto from the several beams are in phase. For example, if a device includes four anode plates, as shown in Fig. 1, alternate plates may be electrically connected together as shown.

As shown in Fig. 2, the invention may be embodied also in electron discharge devices having coaxially arranged electrodes. In this figure elements corresponding to the elements shown in Fig. 1 are similarly designated except as using a different subscript. In this embodiment, the cathode I02 may be a single linear filament or a plurality of filaments arranged in a cylindrical boundary, and the focussing electrode I32 may comprise a plurality of metallic linear wires or rods which are equally spaced, parallel to each other and to the cathode I02, and are arranged in a cylindrical boundary about and coaxial with the cathode. The accelerating electrode I52 may include a plurality of arcuate plates arranged in a cylindrical boundary coaxial with the cathode I 02. The elements of the control electrode I22, which may be wires or rods disposed parallel to each other and to the cathode I 02, are disposed in a cylindrical boundary coaxial with the cathode I02, these elements being electrically connected together by means not shown similarly as in Fig. 1. Likewise, the elements of the focussing electrode I42 may be linear wires or rods disposed parallel to each other and to the cathode I02 and arranged in a cylindrical boundary coaxial with the cathode I02. The anodes II2 may be arcuate plates having overlapping end portions and forming a substantially cylindrical enclosure coaxial with the cathode I02, alternate plates being electrically connected together similarly as in Fig. 1 by means not shown. The several electrodes, it will be apparent, are arranged to provide unimpeded radial paths for electrons to the overlapping edges of the anodes.

The paths traversed by electrons in the device shown in Fig. 2 will be clear, it is believed, from the detailed description hereinabove with reference to Fig. 1.

In the typical oscillator circuit illustrated in Fig. 3, the anodes II are connected to opposite ends of an inductance 35 which is shunted by a suitable variable condenser 36 to constitute the whole a tuned circuit. Similarly, corresponding elements of the control electrode l2 are connected to opposite ends of an inductance 31, which is in parallel with a variable condenser 38. The midpoint of the inductance 31 is connected to the negative terminal of the source 3| through a resistance 39 shunted by a condenser 40.

At ultra-high frequencies, because of the electron transit times, a time delay may occur between the potential changes on the elements of the control electrode l2 and the corresponding deflections of the electron beams at their points of focus upon the anodes II. This time delay may be counteracted by slightly detuning either the control electrode or anode circuit by varying the condenser 38 or 36, respectively. The requisite shifting in the phase of the alternating potentials upon the control electrode l2 and anodes H to counteract the time delay may be obtained also by coupling the inductances 35 and 31 by a suitable time delay circuit such as a short transmission line 4|, suitable stopping condensers 42 being connected in series with the line 4|.

Although specific embodiments of this invention have been shown and described it will be understood, of course, that various modifications may be made therein without departing from the scope and spirit of this invention as defined in the appended claims.

What is claimed is:

l. A wave generator comprising an electron discharge repeater device having input and output electrodes, and a feed-back means coupling said output electrodes with said input electrodes, said means comprising, with the inherent impedances of said device, frequency determining means whereby the frequency is so high that the electron transit time is finite and a material part of the generated wave cycle and comprising also a transmission line for shifting the phase of the fed-back wave at the input electrodes to any desired degree dependent on the efficient operation of the circuit as a whole without substantial effect on the characteristic generator frequency.

2. The generator specified in claim 1 in which said electron discharge repeater device is of the electron beam type.

3. A wave generator comprising in combination, an electron discharge device comprising a cathode, a pair of anodes, means including a control electrode for deflecting an electron beam alternately to said anodes, a circuit connecting said anodes and said cathode, another circuit connecting said cathode and said control electrodes, and means comprising a transmission line coupling said circuits and adaptedto determine the generated wave frequency, said frequency being so high that the electron transit time is finite and a material part of the wave cycle, said transmission line being adapted for shifting the phase of the potentials appearing on said anodes relative to the potentials appearing on said control electrode to an extent surlicient to compensate for the dephasing effect resulting from the finite electron transit time without substantial effect on the characteristic generator frequency.

4. A wave generator comprising in combination, an electron discharge device comprising a cathode, a pair of anodes, means including a control electrode for deflecting an electron beam alternat'ely to said anodes, a tuned circuit connecting said cathode and said anodes, a tuned circuit connecting said cathode and said control electrode, each of said tuned circuits being tuned to the characteristic generator frequency, said frequency being so high that the electron transit time is finite and a material part of the generator wave cycle, and a transmission line coupling said tuned circuits for shifting the phase of the potentials on said anodes relative to the potentials on said control electrode to an extent suflicient to compensate for the dephasing efiect resulting from the finite electron transit time.

RAYMOND A. HEISING. 

